The man, whose name has not yet been identified, allegedly ran from the apartment carrying a 1-year-old child before he was caught by officers, police said.

The male was wanted on assault charges, and Gaines was wanted on an arrest warrant for an incident in March for which she was criminally charged with disorderly conduct, resisting arrest, and various traffic charges.

Police reportedly knocked on the apartment multiple times, identified themselves, and said they heard a man and woman's voice inside the residence. After repeated attempts to enter the home, one officer got a key from the landlord and opened the apartment. The officer saw Gaines sitting on the floor, pointing a shotgun at him. She had her five-year-old son in her arms, Johnson said.

"The officers ... immediately summoned tactical personnel who began hours-long dialogue with [Gaines]," Johnson said. "During that dialogue and conversation, she repeatedly pointed a long gun at the police officers. ... At around 3pm this afternoon, Gaines pointed the long gun at personnel and advised them that if they did not retreat or leave, she was going to kill them."

"Tragically, the child who was also in the dwelling, was struck by a round," Johnson said.

Gaines' uncle, Jermaine Barnett, told the Baltimore Sun that the child was Gaines' son. Police say he was shot in a limb during the stand-off and was transported to a local hospital with non-life-threatening injuries.

Police do not know if the round the child was struck with was fired by officers or Gaines.

"We are of course extremely upset at an event like this," police spokeswoman Elise Armacost said at press conference. "We do not like to be in a position of having to use lethal force, but this was a situation where our officers exercised patience for hours and hours. ... We are very relieved the child was not seriously injured."

Another one of Gaines' uncles, Jerome Barnett, told the Sun that his niece "was feisty, but she was smart and she was respectful. ... My niece is a good person; I never knew her to be a rowdy person."

Gaines' death has sparked outrage on Twitter, with many demanding to know if the officers involved were wearing body cameras.

According to the Dallas Morning News, all officers involved were placed on administrative leave and the department did not give the races of the officers. Their names are expected to be released 48 hours after the incident.

This article contains explicit descriptions of deadly violence. Philando Castile of Minnesota was shot Wednesday night by police officers during a traffic stop in Falcon Heights while his girlfriend captured the graphic aftermath on Facebook Live .